Television apparatus



July 11, 139, giHgLp/ggs 2,1 35,74

TELEVISION APPARATUS Filed Sept. 30, 1935 2 Sheets-Sheet l 5 RE! sou/v17soumzw CHER/El? PICTURE CHER/ER L r". AMP.

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Witness R. s. HOLMES 2,1653% TELEVIS ION APPARATUS new i INVEN'I'OREalphS. Holmes Patented July 11, 1939 TAT TELEVISION APPARATUS ofDelaware Application September 30, 1935, Serial No. 42,908

8 Claims.

My invention relates to television apparatus and particularly toreceiving apparatus adapted to receive pictures accompanied. by sound.

In Carlson Patent 1,975,056 there is described a system for thetransmission of television pictures and a the accompanying sound signalin which the picture signal is transmitted on one carrier wave and thesound signal is transmitted on a separate carrier wave a fixed frequencyaway from it. In the receiver the two carrier waves are passed through abroadly tuned radio frequency circuit to a detector. The detector iscoupled to a local oscillator which heterodynes the carrier waves toproduce two intermediate frequency signals, the beats between theoscillator and the picture carrier wave and between the oscillator andthe sound carrier wave.

The two intermediate frequency signals are amplified in two intermediatefrequency amplifiers, rectified, and the rectified signals supplied tothe cathode ray receiver tube and to the loud speaker.

A receiver such as that described above is entirely satisfactory, but itis inherently more costly than a receiver which reproduces the picturewithout the accompanying sound, on account of the additional functionsit performs.

Since it is desirable to produce a television receiver of low cost itwould be desirable to limit the requirements of the receiver to theproduction of the picture without the accompanying sound, provided thesound accompaniment can be obtained in some other suitable manner.

Assuming that the television picture and the accompanying sound aretransmitted on separate carriers, as described in the Carlson patent, astraight picture receiver could be built at low cost, and the soundcould be picked up on a standard broadcast receiver by using a suitableconverter to change the transmitted sound carrier to a broadcastfrequency, where it could be amplified and reproduced in the normalmanner by the broadcast receiver. The disadvantage of such a system isthat there are two tuning controls to be adjusted when tuning in astation, the regular picture receiver control and the tuning of theconverter or of the broadcast receiver for sound. A further disadvantageis that there is no reference for tuning the picture receiver. Thepicture receiver has a wide frequency band, and unless there is somereference to tune by, other than the appearance of the picture itself,it is very difilcult, if not impossible, to properly tune the receiver.

It is, accordingly, an object of my invention to provide a method of andmeans for operating a regular broadcast receiver in conjunction with atelevision receiver designed to receive picture signals only withoutencountering the abovementioned disadvantages.

It is a further object of my invention to provide means whereby a singleantenna connected to the television receiver may be employed for Ieither the reception of picture signals or for the reception of soundprograms in the broadcast band by a broadcast receiver.

It is still a further object of my invention to provide an improvedmeans for operating a television receiver and a broadcast receiver inconjunction with a minimum of switching.

In one of the preferred embodiments of my invention the televisionreceiver unit is designed to operate in conjunction with a multi-bandbroadcast receiver having what is commonly referred to as the C band.The C band includes the 25 meter band, the 49 meter band, and severalothers. The television receiver is so designed that the soundintermediate frequency falls within the C band, say at 9 megacycles.This intermediate frequency signal is fed to the broadcast receiverwhich is switched to the C band and tuned to 9 megacycles, Thus thetuning of the broadcast receiver is fixed and the desired televisionstations are tuned in by operating the single tuning knob on thetelevision receiver.

Preferably a circuit and switching arrangement is employed which causesthe television receiver short wave antenna to function as a broadcastantenna for the broadcast receiver when the television receiver powerswitch is turned to the off position.

Other objects, features and advantages of my invention will appear fromthe following description taken in connection with the accompanyingdrawings in which,

Figure 1 is a schematic diagram of one embodiment of my invention;

Fig. 2 is a circuit diagram of an embodiment of my invention; and

Figs. 3 and 4 are circuit diagrams of other embodiments of my invention.

Referring to Fig. 1, at i there is indicated a television receiverhaving input terminals 2 and 3 connected through a. transmission line 5to a suitable short wave antenna l such as an antennaof the dipole type.The end of a cathode ray tube upon which the picture appears isindicated at 6. The receiver is provided with an on-01f switch 1 (Fig.3) which preferably may be operated by the same knob 3 that controls thebrightness of the picture, or some other characteristic thereof, such asdetail.

In a preferred embodiment of the invention, which will be describedlater, the same knob 8 which operates the on-off or power switch alsooperates an antenna switch 9 (Fig. 3) for the purpose of making theantenna 4 function as a short wave antenna when the power switch is onand as along wave antenna when the power switch is off. The tuning knobof the television receiver is indicated at H.

The television receiver I is provided with an output terminal I2 forconveying the sound signals accompanying the picture signals to abroadcast receiver of conventional design indicated at I3. One inputterminal I4 (the ground post) of the broadcast receiver I3 is connectedto ground while the other input terminal l6 (the antenna post) may beconnected through a switch arm II either to a long wave or broadcastreceiving antenna I8 or to a contact point I9 which is connected to thesound output terminal I2 of the television receiver I.

The broadcast receiver I3 is provided with the usual loud speaker 2|,power switch 22, Wave band switch 23 and tuning dial 24.

The circut diagram for the apparatus shown in Fig. l is shown in Fig. 2.Referring to this figure, the television receiver comprises a tunableselecting circuit 23 which is tuned broadly enough to pass both thesound carrier and the picture carrier radiated from a transmittingstation. The selecting circuit 25 consists of two coupled tuned circuits21 and 28 each of which may be shunted by a resistor for the purpose ofbroadening the tuning. A suitable short wave antenna, indicated by aconventional symbol at 29, is coupled to the input side of the selectingcircuit 26.

The output side of the selecting circuit 26 is connected to the inputterminals of a first detector 3|, this detector being coupled to atunable oscillator 32 for the purpose of heterodyning the incomingcarrier waves to intermediate frequency signals. The selecting circuit26 and the oscillator 32 may be tuned simultaneously by the singletuning knob II in accordance with usual practice.

The intermediate frequency picture signal is transferred from the outputcircuit of the first detector 3| through a secondary winding 34 of abroadly tuned intermediate frequency transformer to an intermediatefrequency amplifier'36, and through another broadly tuned intermediatefrequency transformer 31 to such other intermediate frequency amplifiersas are necessary. After suitable amplification, the intermediatefrequency picture signal is detected in a second detector to obtain thepicture signal which is then amplified and supplied to the cathode raytube 6.

The intermediate frequency sound signal which appears in the outputcircuit of the first detector 3| is transferred to a comparativelysharply tuned secondary winding 38, which is loosely coupled to thedetector output circuit, and fed to the sound output terminal I2. Theconventional broadcast receiver I3 may then be connected either to thelong wave length antenna for receiving ordinary sound broadcast programsor to the output terminal I2 for receiving the sound accompanying thepicture, as previously explained.

It will be understood that when receiving television programs the tuningof the broadcast receiver is fixed and that all tuning is done by meansof the single tuning knob I I on the television receiver. In operatingthe picture receiver unit I and the broadcast receiver I3 inconjunction, the switch ll is moved to the position indicated in Figs. 1and 2 and the band switch 23 is turned to the desired band such as the Cband. The broadcast receiver I3 is then tuned to a predeterminedposition which may be marked on the tuning dial 24 by the letter T asindicated in Fig. l'to tune the broadcast receiver to the intermediatefrequency sound signal.

It will be apparent that it is desirable to eliminate the long waveantenna I8 and connect the broadcast receiver I3 permanently to thetelevision receiver I whereby operation of one switch is eliminated.This may be accomplished by means of a circuit such as shown in Fig. 3in which parts similar to those in Figs. 1 and 2 are indicated by thesame reference numerals. Re-

' ferring to Fig. 3 the television input terminals 2 and 3 are connectedto a suitable short wave antenna such as an antenna of the dipole typeor an antenna of the Zeppelin or voltage fed type. The input terminals 2and 3 are connected to an input coil 39 which is coupled to a tunableselecting circuit 4| comprising two coupled resonant circuits. Aspreviously described, the selecting circuit is tuned broadly enough topermit both the sound carrier and the picture carrier to pass thereunderto a first detector.

The tunable oscillator 32 heterodynes the incoming signals tointermediate frequency signals. The intermediate frequency picturesignal is taken from the output circuit of the first detector 3i bymeans of a tuned circuit 42. The signal is then suitably amplifiedin'intermediate frequency amplifiers, detected, and again amplified andsupplied to the cathode ray tube 6.

The intermediate frequency sound signal is taken from the output circuitof the first detector 3! by means of a coil 33 which is coupled theretoand which has one end connected to the midpoint of the input coil 39through a conductor 44. The other end of the coil 13 is connected to thesound output terminal i 2 of the television receiver.

The antenna post I6 of. a multi-band broadcast receiver 13 such aspreviously described is connected through a shielded conductor 36 to thesound output terminal i2 of the television receiver. The ground post I4of the broadcast receiver is connected to ground in the usual manner.

The antenna switch 9 is provided which when closed, or in the onposition, connects the midpoint of the input coil 39 to ground.

Filament current and a suitable direct current voltage are supplied tothe television receiver from any suitable power supply such as a 110volt line. This line is shown connected through the power switch "I tothe primary winding of a transformer 41. A low voltage secondary winding48 is. connected to the heater filaments of the various vacuum tubeswhich filaments may be connected in parallel as shown in the drawings. Ahigh voltage secondary winding 49 is connected to a suitable rectifierand filter unit indicated at for supplying the necessary direct currentpotentials.

As described in connection with Fig. 1, the antenna switch 9 preferablyis interlocked or connected to the power switch I whereby the twoswitches. are operated simultaneously by the actuation of a single knobsuch as the knob 8 shown in Fig. 1. r

From the foregoing description, it will be seen that when the powerswitch is tuned on, the midpoint of the input' coil 39 is connected toground whereby the dipole antenna 4 (Fig. 1) or other short wave antennaconnected to the input terminals 2 and 3 will function in the usualmanner as a short wave antenna to supply the high frequency sound andpicture carrier to the selecting circuit 4|. In this case, theintermediate frequency sound signal will be transferred from thedetector output circuit to the coupling coil 43 and through the shieldedconductor 46 to the input terminals of the broadcast receiver l3.Therefore, the picture signal will be received by the televisionreceiver unit i and the accompanying sound will be received by thebroadcast receiver 13.

When the power switch of the television receiver is turned off, themidpoint of the input coil 39 will no longer be grounded and the shortWave antenna d and the transmission line 5 (Fig. 1) connecting it to theinput terminals 2 and 3 will function as a long wave antenna. Therefore,sound signals within the broadcast range will be supplied through theconductor 44, the coupling coil 43 and the shielded conductor dB to theantenna terminal iii of the broadcast receiver. It will be apparent thatby utilizing this circuit and switching arrangement I not only avoid thenecessity of employing two separate antennas but I also simplify theoperation of the television and broadcast receiver units.

Referring to Fig. 4, there is shown an embodiment of my invention inwhich the intermediate frequency sound signal is transmitted over atransmission line 52 to the sound unit. Like parts in Figs. 3 and 4 areindicated by the same reference numerals. It the sound unit indicated at53 is a broadcast receiver, as in the previously described receivingsystems, the switch 9 is employed for grounding the midpoint of theinput coil 39 during the reception of television signals. When theswitch is in this position, as shown in the drawings, the intermediatefrequency sound signal is transferred from the output circuit of thedetector 3! to the coil 43 and is transmitted over the two transmissionline conductors 54 and 56 to the sound unit 53. When the switch 9 isopen, the short wave antenna and its transmission line function as along wave antenna, as previously described, and the comparatively lowfrequency sound modulated carrier waves pass through the inductance coil43, over the conductor 54 to the sound unit 53 and back through theother conductor 56 to ground at a point in the television receiver.

It has been found that under certain circumstances it is desirable toemploy a transmission line inside a television receiver cabinet itself.It has been the usual practice to mount the picture signal apparatus andthe sound signal apparatus on a common chassis. Greater flexibility inreceiver design is possible if the sound unit and the picture unit arebuilt on separate chassis. By employing this design, sound units capableof reproducing sound with either moderate or high fidelity may becombined with picture receiver units which likewise may be capable ofreproducing pictures with either moderate or high fidelity.

It is possible to employ two separate reproducing units in a singlereceiver cabinet, as described above, by employing a transmission linefor transferring the intermediate frequency sound signal from the firstdetector to the sound unit.

When this receiver design is employed, the switch 9 is replaced by apermanent connection and the sound unit 53 consists of a plurality ofintermediate frequency amplifiers, a second detector and an audiofrequency amplifier.

While it is preferred to employ a short wave antenna connected through atransmission line to an input coil grounded at its midpoint, fairly goodpicture signal reception may be obtained by connecting an antenna toonly one end of the input coil. In that case, one half of the input coilis not used.

From the foregoing description it will be apparent that various othermodifications may be made in my invention without departing from thespirit and scope thereof and I desire, therefore, that only suchlimitations shall be imposed there on as are necessitated by the priorart and are set forth in the appended claims.

I claim as my invention:

1. In combination, a television receiver and a broadcast sound receiver,a short wave antenna, a transmission line connecting said antenna tosaid television receiver, and switching and circuit means forselectively utilizing said antenna as a short wave antenna for saidtelevision receiver or said antenna and said transmission line incombination as a long wave antennna for said broadcast receiver.

2. In combination, a television receiver and a broadcast sound receiver,an input coil in said television receiver, a short wave antenna, atransmission line connecting said antenna to said input coil, aconnection between said input coil and said broadcast receiver, andmeans including a switch for grounding the midpoint of said input coilfor selectively utilzing said antenna as a short wave antenna for saidtelevision receiver or said antenna and said transmission line incombination as a long wave antenna for said broadcast receiver.

3. The invention according to claim 2 characterized in that saidtelevision receiver includes a power switch and means for so connectingsaid power switch to said first switch that said midpoint is grounded inresponse to said power switch being turned on and disconnected fromground in response to said power switch being turned ofi.

4. In combination, a television receiver comprising an input coil atleast one end of which is to be connected to an antenna and a point onwhich is to be connected to ground, means for converting incomingpicture and sound carrier waves to intermediate frequency picture andsound signals, means comprising a selecting circuit for transferringsaid incoming carrier Waves from said input coil to said convertingmeans when said point is grounded, a broadcast sound receiver, meansincluding an inductance coil for coupling the output circuit of saidconverting means to said broadcast receiver whereby said intermediatefrequency sound signal is transferred thereto when said point isgrounded, said coupling means including a connection from one end ofsaid inductance coil to an input terminal of said broadcast receiver, aconnection from said point to the other end of said inductance coil, andan antenna switch for connecting said point to ground when desired.

5. In combination, a television receiver comprising an input coil havingantenna terminals and a midpoint, means for converting an incomingsignal to an intermediate frequency signal, means comprising a selectingcircuit for transferring said incoming signals from said input coil tosaid converting means when said midpoint is grounded, a broadcast soundreceiver, coupling means for coupling the output circuit of saidconverting means to said broadcast receiver whereby an intermediatefrequency is transferred thereto when said midpoint is grounded, aconnection from said midpoint to said coupling means whereby signals aretransferred directly from said coupling coil to said broadcast receiverwhen said midpoint is not grounded, and an antenna switch forselectively connecting or disconnecting said midpoint to or from ground.

6. The invention according to claim 5 characterized in that thetelevision receiver is provided with a power switch for energizing it,and further characterized in that said antenna switch and said powerswitch are so connected that when said power switch is 7 closed saidmidpoint is grounded and when said power switch is open said midpoint isnot grounded.

7. The invention according to claim 5 characterized in that saidcoupling means comprises an inductance coil having one end connected tosaid midpoint and the other end connected to an input terminal of thebroadcast receiver.

8. In a radio receiver for receiving signals from a short wave energycollector through a transmission line, a broadly tuned frequencyconvertor portion, a relatively sharply tunable beat-frequency amplifierportion, and switching and circuit means for effecting a connection fromsaid energy collector to either portion, said means including a couplingwinding adapted to be conn'ected at each end through said transmissionline to said energy collector, a coupling circuit connected to themidpoint of said winding and to said beat-frequency amplier portion,said switching means including contacts for grounding said midpoint ofthe coupling winding when receiving short wave signals.

RALPH S. HOLMES.

